An organic LED (Light Emitting Diode) element has been widely used for displays, backlights, lighting applications, and the like.
A common organic LED element has a first electrode (anode) placed on a substrate, a second electrode (cathode) and an organic layer placed between the electrodes. When a voltage is applied between the electrodes, holes and electrons are injected from respective electrodes to the organic layer. When the holes and the electrons are recombined in the organic layer, binding energy is generated and an organic light-emitting material in the organic layer is excited by the binding energy. Since light is emitted at the time when the excited light-emitting material is returned to a ground state, a light emitting (LED) element is obtained by utilizing the light emission.
Usually, for the first electrode, i.e., anode, a transparent thin film such as ITO (Indium Tin Oxide) is used and, for the second electrode, i.e., cathode, a metal thin film such as aluminum or silver is used.
Recently, it has been proposed to place a resin-made light scattering layer having scattering materials between an ITO electrode and a substrate (for example, Patent Document 1). In such a constitution, since a part of emitted light generated in the organic layer is scattered by the scattering materials in the light scattering layer, a quantity of light confined in the ITO electrode and substrate (a quantity of totally reflected light) decreases and thus a light extraction efficiency of the organic LED element can be enhanced.